So I found out some new information on the motor that is in our Project '68 Cutlass. The car has been around the family for about 10 years now and has changed hands, and now my son and I are gonna try and get it running and finished up to be a driver. But today, I found out that the block that is in the car is a 1970 Block ID: 30Mxxxxx and the heads are #5 heads... Now from what I have read, is that the 1970 350's were the better blocks of the bunch, and the #5 heads flow the best out of them... I have already swapped the points to an HEI, and I am going back on with Hooker Headers and Summit's 2.5 inch dual exhaust system. We have a freshly rebuilt and tuned Q-Jet and new plugs and wires. I guess what I am wondering is if the previous owner was on to something and used the 1970 short block and topped it with the 64cc higher flowing heads to try and make some better than stock power. What are your thoughts on that concoction?

Tempted to get an RPM intake for it, too, while we are at it.... Next on the list is gearing on the Rear End, and maybe go through the trans and a small converter... This may turn out to be a fun cruiser with not too much invasive work....

Thanks

 

There is no functional difference among any 1968-76 350 blocks. There is also no functional difference among any #4, 5, 6, 7, or 7A heads. The 7 and 7A heads have deeper spring pockets for rotators and hardened valve seats, but performance-wise you won't see a difference if they have the same size valves.

 

Ok, glad you responded Joe, thanks... So I guess we should just keep on rockin and rollin and then do a compression test, and that will at least give us the compression numbers. At least we know it will "Huff and Puff" well..... I'll update as we go...

Thanks...

 

no cam change? that will make a bigger difference coupled with the intake,ignition headers and gearing

 

Replace the timing chain set for performance and reliability. Squeezing performance out of an engine with a stretched chain that retards valve timing coupled with likely an original nylon tooth cam gear about to fail won't go well.

Good luck with the project, great to hear you are working on it with your son!

 

Glad you mentioned that. I thought since the motor will be out to be painted, new motor mounts and header install, I did wonder about doing a cam and lifter swap, especially since reading about the original nylon cam gears.

What is the largest recommended cam that won't bind the stock coils and will work well with basically all stock parts? I have no intentions of getting the heads redone or rebuilding the short block. I don't mind replacing the timing chain and cam and lifters...

Thanks

 

Valve lift is what causes spring bind but duration is what needs to be matched to the compression ratio, rear gearing, etc.

How radical are you looking to go? Do you want driveability or full out race performance?

 

Nice combination there, Kenneth! Are you on stock block and heads?

I'm not looking for daily driver or all out race.... I will be happy with pushing the stock block and heads to a RELIABLE max if that makes sense. In other words, a cam that will extract the most power out of the stock motor without the risk of breaking it...